1. Field of the Invention
The present invention relates to a micro electrode array for measuring bioelectric signals and a method for controlling the same, and more particularly to a high-density micro electrode array and a serial control method thereof.
2. Description of the Prior Art
Owing to advancement of biomedical measurement technology, micro electrodes can help to miniaturize a detector and downsize it, decrease detector power consumption, therefore, they are fit for mass production. The detector has plenty of miniaturized electrode elements, and thus it is feasible to build a micro electrode array measuring platform for measuring a plurality of physiological parameters concurrently.
Referring to FIG. 1, a conventional electrode element 100, basically, comprises an electrode point 101 and a conducting wire 103. The electrode point 101 is the exposed metal portion of the electrode point 101. The electrode point 101 is used in contact with a measurement portion, and it allows the electrode element to receive a signal by a related mechanism, namely electrode-electrolyte interface. Afterward, the signal is sent to a back end via the conducting wire 103 for further processing. The conducting wire 103 is required to be insulated very well so as to ensure the effective delivery of the signal. Given its aforesaid basic structure, the electrode element can measure signals in real time so as to maintain high temporal resolution.
Owing to the presence of the basic structures in a micro electrode array, the basic structures must be insulated from each other in order to prevent crosstalk between different signals. To ensure high yield of a detection chip, the distance between any two basic structures (including the electrode point and the conducting wire) has to be the minimum space set forth in the design rule of a fabrication process so as to enable smooth transmission of signals by the conducting wire to a back end for further processing. However, the space limitation affects spatial resolution.
Both temporal resolution and spatial resolution are important to related application of a micro electrode array. Take recording neural signal network, for example, it requires its spatial resolution to be one or two neurons in order to evaluate the route whereby neural electrophysiological signals are transmitted. Regarding application of electrical stimulation, appropriate spatial resolution can ensure precise electrical stimulation at one or more points, but prevents unnecessary portions to be electrical stimulated. Take human interface for example, high precision of signal resolution is required.
FIG. 2 shows a schematic view of conventional layout of electrodes in one dimension, the electrode point 101 has to be connected to the conducting wire 103 so as to transmit an electrical signal. Regarding a conventional electrode array, the electrode points have positive correlation with the conducting wires in quantity, primarily because each of the electrode points has to be connected to a conducting wire. Hence, the number of the electrode points deployed is limited by the area of a substrate 201. On the other hand, spatial resolution of a micro electrode array depends on the number of the electrode points. Therefore, the layout of a conventional micro electrode array is a hindrance to the optimization of spatial resolution.
On the other hand, some detection chips have to penetrate biological tissue, and the cross-section of the path of penetration (an electrode structure of one dimension) should be small so as to minimize any injury done to the biological subject. However, given a conventional layout, increasing spatial resolution definitely conflicts with the reduction of the cross-section of the path of penetration into biological tissue. Hence, to implement a conventional high-density micro electrode array, a large cross-section of the path of penetration into biological tissue is inevitable.
A conventional micro electrode array is disclosed in U.S. Pat. No. 5,388,577, entitled Electrode Array Microchip, and, another conventional micro electrode array is taught in Taiwanese Patent Publication No. 200628797, entitled Multiple-Channel Micro Electrode Probe and Method for Fabricating the Same”, wherein the conventional micro electrode arrays comprise similar basic structure as described above. Although, the conventional micro electrode array has an advantage of real-time measurement. However, the conventional layout, which features a conducting wire and an electrode, brings a new problem, namely low spatial resolution in the presence of a limited cross-sectional area of a detection chip.
Therefore, the structure of a conventional micro electrode array, coupled with design rules, limits the spatial resolution of the micro electrode array greatly and, more particularly, puts implanted elements (penetration described above) at disadvantageous position because they are desirably downsized, but their spatial resolution is unlikely to increase.